The study of appetite in humans has previously been confined to the use of visual analog scales and food intake measurements. With the use of new brain imaging techniques, we can now examine brain activity in response to food stimuli in vivo. We have recently developed and tested a functional magnetic resonance imaging (fMRI) protocol to study brain responses to food stimuli. We propose to use this protocol to examine and compare brain responses to food stimuli in lean and obese subjects in the fasted and fed states. Twelve lean and 12 obese women will be scanned after an overnight fast and after a standard meal. The fMRI protocol will consist of a block design in which subjects will be scanned when viewing real foods and non- food items and when touching foods and non-food items. After the fasting fMRI protocol, lean and obese subjects will consume a liquid meal providing them with 35% of their estimated energy requirements. The meal will be consumed within a 20-minute period and the subsequent fMRI scan will be taken 30 minutes following meal consumption. Brain regions that are more robustly activated both visually and tactilely with food but not also activated visually and tactilely with non-foods will be considered to be activated due to foods. These studies will allow us to examine differences in individual's brain responses based on their body weight and feeding status. If brain responses to food stimuli are different between lean and obese individuals, the long-term goals are to determine whether the brain responses of obese individuals to food stimuli can be modified with weight loss and to examine whether there are differences in brain responses to food stimuli between healthy lean individuals and anorexics. Results of this study will help create the foundation for the study of integrative responses to foods at the whole brain level in humans and will set the stage for a series of innovative experimental paradigms. [unreadable] [unreadable] [unreadable]